Centrifugal fan

Abstract

A side wall of a centrifugal fan includes a gap expanding portion arranged to gradually expand a gap between an impeller and the side wall from an upstream end toward a downstream end with respect to a rotation direction of a rotating portion. In the centrifugal fan, an electronic component arranging portion of a board is arranged in an area surrounded by the gap expanding portion, the impeller, and an air outlet, and accordingly does not overlap with a motor or the impeller in an axial direction. The electronic component arranging portion is arranged in an area extending, in a circumferential direction about a central axis, from a position 180 degrees upstream from a middle of the air outlet downstream to the middle of the air outlet, that is, in an area where a wind channel has a large width.

What is claimed is: 
     
         1 . A centrifugal fan comprising:
 a motor including a rotating portion, and arranged to rotate the rotating portion about a central axis extending in a vertical direction;   an impeller arranged to rotate together with the rotating portion;   a board arranged to supply a drive current to the motor; and   a housing arranged to accommodate the rotating portion and the impeller, and including an upper air inlet and an air outlet; wherein   the housing includes:
 a bottom plate arranged to spread substantially perpendicularly to the central axis on a lower side of the impeller; 
 a top plate arranged to spread substantially perpendicularly to the central axis on an upper side of the impeller; and 
 a side wall arranged to join an outer edge portion of the bottom plate and an outer edge portion of the top plate to each other on a radially outer side of the impeller; 
   the side wall includes a gap expanding portion arranged to gradually expand a gap between the impeller and the side wall from an upstream end toward a downstream end with respect to a rotation direction of the rotating portion;   a circumferential extent of the gap expanding portion is arranged to be at least half a circumferential extent of the entire side wall;   the side wall includes a pair of edges arranged, respectively, on a downstream side and on an upstream side with respect to the rotation direction;   an opening between the pair of edges is the air outlet;   the top plate includes the upper air inlet over the motor;   the board includes:
 an electronic component arranging portion arranged to have one or more electronic components arranged thereon; 
 a motor connection portion arranged to extend from the electronic component arranging portion toward the motor; and 
 a draw-out portion arranged to extend from the electronic component arranging portion to an outside of the housing; 
   the electronic component arranging portion is arranged in a predetermined area on the bottom plate; and   the predetermined area is an area surrounded by the gap expanding portion, the impeller, and the air outlet, and extending, in a circumferential direction about the central axis, from a position 180 degrees upstream from a middle of the air outlet downstream to the middle of the air outlet.   
     
     
         2 . The centrifugal fan according to  claim 1 , wherein the board is a flexible printed circuit board. 
     
     
         3 . The centrifugal fan according to  claim 1 , wherein a distance between the electronic component arranging portion and the side wall is arranged to be smaller than a distance between the electronic component arranging portion and the impeller. 
     
     
         4 . The centrifugal fan according to  claim 2 , wherein a distance between the electronic component arranging portion and the side wall is arranged to be smaller than a distance between the electronic component arranging portion and the impeller. 
     
     
         5 . The centrifugal fan according to  claim 3 , wherein the electronic component arranging portion is arranged in a vicinity of the edge of the side wall on the downstream side with respect to the rotation direction. 
     
     
         6 . The centrifugal fan according to  claim 4 , wherein the electronic component arranging portion is arranged in a vicinity of the edge of the side wall on the downstream side with respect to the rotation direction. 
     
     
         7 . The centrifugal fan according to  claim 1 , wherein the housing includes, separately from the upper air inlet and the air outlet, a draw-out opening through which the draw-out portion is arranged to be drawn out of the housing. 
     
     
         8 . The centrifugal fan according to  claim 7 , wherein the draw-out opening is arranged radially inward of a radially outer end portion of the impeller in a plan view. 
     
     
         9 . The centrifugal fan according to  claim 7 , wherein the draw-out opening is arranged radially outward of a radially outer end portion of the impeller in a plan view. 
     
     
         10 . The centrifugal fan according to  claim 9 , wherein the draw-out opening is defined in the side wall. 
     
     
         11 . The centrifugal fan according to  claim 7 , wherein
 the impeller includes an annular impeller base portion fixed to the rotating portion, and a plurality of blades arranged to extend radially outward from the impeller base portion; and   the draw-out opening is arranged radially inward of a radially outer edge portion of the impeller base portion in a plan view.   
     
     
         12 . The centrifugal fan according to  claim 1 , wherein the electronic component arranging portion is arranged in an area extending, in the circumferential direction about the central axis, from a position 90 degrees upstream from the middle of the air outlet downstream to the middle of the air outlet. 
     
     
         13 . The centrifugal fan according to  claim 1 , wherein
 the bottom plate includes a lower air inlet arranged under the motor or the impeller; and   the draw-out portion is arranged to be drawn out of the housing through the lower air inlet.   
     
     
         14 . The centrifugal fan according to  claim 1 , wherein
 the bottom plate includes a plurality of lower air inlets each of which is arranged under the motor or the impeller, and a rib arranged between adjacent ones of the lower air inlets; and   the draw-out portion is arranged to extend along the rib.   
     
     
         15 . The centrifugal fan according to  claim 1 , wherein the draw-out portion is arranged to be drawn out of the housing through the air outlet. 
     
     
         16 . The centrifugal fan according to  claim 1 , wherein
 the motor connection portion includes land portions to which windings of the motor are connected; and   at least one of the land portions is arranged in an area extending, in the circumferential direction about the central axis, from the position 180 degrees upstream from the middle of the air outlet downstream to the middle of the air outlet.   
     
     
         17 . The centrifugal fan according to  claim 16 , wherein wires connecting the one or more electronic components on the electronic component arranging portion and the land portions to each other are each arranged to extend without bending at an acute angle. 
     
     
         18 . The centrifugal fan according to  claim 1 , further comprising a potting portion made of a resin, and arranged to cover the electronic component arranging portion.